URL Redirection:
URL redirection, also called URL forwarding is a technique on the World Wide Web for making a web page available under many URLs. There are several ways to redirect a URL including (a) Showing a page with a link and asking the user to manually click on it (b) HTTP redirect (c) javascript redirect (d) using .htaccess files (e) using HTTP Meta and Refresh tags and (e) Frame redirect where one frame shows the redirected page
URL Shortening:
URL shortening is a technique on the World Wide Web where a provider makes a web page, typically owned by another entity, available under a short URL in the provider's domain, in addition to the original address. tinyurl.com is one of the companies that offers this service. For example, the
page http://en.wikipedia.org/w/index.php?title=TinyURL&diff=2836210 22&oldid=283308287 points to http://tinyurl.com/mmw6lb.
The provider controls the domain of the rewritten URL and hence has the ability to track and maintain access to the original web page through the rewritten URL.
SMTP Proxy:
An SMTP proxy is an email system that receives emails from the user and sends it to another email system. When SMTP proxies are placed on the outgoing network, they typically are used to intercept all SMTP connections to make sure that unauthorized e-mail, spam, e-mail worms, etc. are not sent from the network.
Web Email:
Web email systems such as Google or Yahoo are used by millions of people worldwide. These systems create private URLs for attachments and images in the emails. They make sure that these private URLs are accessible only to the people who sent and received the message, and not accessible to others. These systems show those private links outside the email message body when the message is displayed on the browser. When an email is sent to another system, they embed the attachment in the message in an encoded form as specified in the MIME specifications RFC 2045 and RFC 2822.
Social Bookmarking:
A social bookmarking system allows users to save links to web pages that they want to remember and/or share. These bookmarks are usually public, and can be saved privately, shared only with specified people or groups, shared only inside certain networks, or another combination of public and private domains. These bookmarks can also be emailed to others. Digg, Delicious, Reddit, Google Bookmarks and Yahoo Bookmarks are some of the popular social bookmarking sites.